Preparation of a lead-free primary explosive

ABSTRACT

Described are compounds and materials that may be used as a lead-free primary explosive, such as copper(I) nitrotetrazolate. Copper(I) nitrotetrazolate may he prepared by a process comprising the steps of: combining cupric salt, water and 5-nitrotetrazolate salt to form a mixture, heating the mixture, adding a reducing agent and stirring with continued heating. The method may also include combining cupric chloride, sodium 5-nitrotetrazolate and sodium ascorbate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/691,849entitled “Preparation of a Lead-Free Primary Explosive,” filedJan. 22, 2010, allowed, which is a continuation-in-part of U.S. patentapplication Ser. No. 11/676,846, entitled “Lead-Free Primary ExplosiveComposition and Method of Preparation,” filed Feb. 20, 2007, now U.S.Pat. No. 7,833,330, which claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/800,816, entitled “Lead-Free Primary ExplosiveComposition and Method of Preparation,” filed May 16, 2006, expired, andclaims the benefit of U.S. Provisional Patent Application Ser. No.61/146,700, entitled “Preparation of a Lead-Free Primary Explosive,”filed Jan. 23, 2009, expired, the entire contents of each of which areincorporated herein by these references.

FIELD OF THE INVENTION

This invention relates to explosives, and in particular to preparationof a primary explosive that is free of lead.

BACKGROUND OF THE INVENTION

Explosive materials have a wide variety of applications. Primaryexplosives are sensitive explosive materials that are used, inrelatively small quantities, to initiate a secondary or main explosivecharge. Primary explosives should be sufficiently sensitive to bedetonated reliably but not so sensitive as to be exceedingly dangerousto handle. Moreover, primary explosives should have sufficient thermalstability so as to not decompose on extended storage or temperaturefluctuation. Many primary explosives in current use contain lead, withthe most well-known example being lead azide. These lead-containingexplosives are undesirable from an environmental standpoint, since theiruse and manufacture can contribute to or cause lead contamination.

Thus, there is a need in the art for lead-free explosive materials andin particular for lead-free primary explosives. Certain lead-freeprimary explosives have been proposed. For instance,nitrotetrazole-based primary explosives have been proposed in U.S. Pat.Nos. 4,093,623 and 4,094,879, as well as in U.S. Patent App. Pub. No.2006/0030715. For a variety of reasons, some of these proposed compoundshave failed to serve as commercially viable substitutes forlead-containing primary explosives, while others exhibit characteristicsthat make them undesirable for at least some commercial applications.For example, U.S. Patent App. Pub. No. 2006/0030715 discloses certainnitrotetrazole complexes (including copper(II) complexes) which form acrystalline structure that is difficult to work with from a handling andordinance loading standpoint.

SUMMARY OF THE INVENTION

Embodiments of the invention are directed to a compound and materialthat may be used as a lead-free primary explosive, and methods forpreparing such compound and material.

In one embodiment, a compound is prepared by the reaction of cupricchloride, sodium 5-nitrotetrazolate, sodium ascorbate, and water.

In another embodiment, a method of preparing a compound suitable as aprimary explosive comprises the steps of: providing a cupric salt;providing a solvent; providing a 5-nitrotetrazolate salt; combining thecupric salt, solvent and 5-nitrotetrazolate salt to form a mixture;heating the mixture; adding a reducing agent; and heating thecombination.

In some embodiments, a compound is prepared by providing cupricchloride; providing water; providing sodium 5-nitrotetrazolate;combining the cupric chloride, water, and sodium 5-nitrotetrazolate toform a mixture; heating the mixture; adding a solution of sodiumascorbate; and heating the combination.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows the results of a differential scanning calorimetry (DSC)analysis on a material prepared according to the present techniques.

FIG. 2 shows the results of a Fourier Transform Infrared Spectroscopy(FTIR) analysis on a material prepared according to the presenttechniques.

DETAILED DESCRIPTION OF THE INVENTION

One aspect of the present subject matter is preparation of the compoundcopper(I) nitrotetrazolate. Also contemplated is any mixture whichcontains copper(I) nitrotetrazolate in a significant quantity (e.g.greater than about 1 weight percent, or alternatively, greater thanabout 5 weight percent).

Methods for preparing copper(I) nitrotetrazolate are contemplated in thepresent application. Copper(I) nitrotetrazolate may be prepared byreacting a copper(II) salt (for example, cupric chloride), a5-nitrotetrazolate salt (for example, sodium 5-nitrotetrazolate) and areducing agent (for example sodium ascorbate) in a solvent (for example,water). Any suitable copper(II) salt, or combination of copper(II)salts, may be employed. Suitable copper(II) salts include, but are notlimited to, cupric chloride and cupric bromide. Likewise, any suitable5-nitrotetrazolate salt, or combination of 5-nitrotetrazolate salts, maybe employed. Suitable 5-nitrotetrazolate salts include, but are notlimited to, sodium 5-nitrotetrazolate and potassium 5-nitrotetrazolate.Likewise, any suitable reducing agent, or combination of reducingagents, may be employed. Suitable reducing agents include, but are notlimited to, sodium ascorbate and ascorbic acid. Likewise, any suitablesolvent, or combination of solvents, may be employed. Suitable solventsinclude, but are not limited to, water, dimethyl sulfoxide (DMSO), aswell as other polar organic solvents.

It will be understood that ionic versions of the salts referred to abovemay be employed in the preparation of copper(I) nitrotetrazolate. Inother words, copper(I) nitrotetrazolate may be prepared by a reaction inwhich copper(I) ions and 5-nitrotetrazolate ions are combined to formcopper(I) nitrotetrazolate.

The components may be reacted under conditions suitable to synthesizecopper(I) nitrotetrazolate. Alternatively, the components may be reactedby mixing them together and then heating the mixture. The mixture may beheated in the temperature range of about 70° C. to about 150° C.,alternatively in the temperature range of about 80° C. to about 130° C.,alternatively to about 100° C. As yet another alternative, a refluxcondenser may be employed, and the mixture may be heated to the refluxpoint. The duration of the heating or refluxing step may be a durationthat is greater than about 1 minute, alternatively greater than about 35minutes, alternatively from about 20 minutes to about 2 hours,alternatively from about 35 minutes to about 1 hour, alternatively about50 minutes.

Regarding quantities of the components employed, 5-nitrotetrazolate maybe supplied in a molar ratio of about 0.5 moles to about 2 moles5-nitrotetrazolate per mole of copper(II). Alternatively,5-nitrotetrazolate may be supplied in a molar ratio of about 0.8 molesto about 1.5 moles 5-nitrotetrazolate per mole of copper(II).Alternatively, 5-nitrotetrazolate may be supplied in a molar ratio ofabout 1 mole to about 1.2 moles 5-nitrotetrazolate per mole ofcopper(II). For example, sodium 5-nitrotetrazolate (NaNT) may besupplied in a molar ratio of about 0.5 moles to about 4 moles NaNT permole of cupric chloride, alternatively about 0.8 moles to about 1.5moles NaNT per mole of cupric chloride, alternatively about 1 mole toabout 1.2 moles NaNT per mole of cupric chloride. Similarly, thereducing agent may be supplied in a molar ratio of about 0.5 mole toabout 2 moles per mole of copper (II). Alternatively, the reducing agentmay be supplied in a molar ratio of about 0.8 moles to about 1.5 molesper mole of copper (II). Alternatively, the reducing agent may besupplied in a molar ratio of about 1 mole to about 1.2 moles per mole ofcopper (II). For example, sodium ascorbate may be supplied in a molarratio of about 0.5 moles to about 4 moles per mole of cupric chloride,alternatively about 0.8 moles to about 1.5 moles per mole of cupricchloride, alternatively about 1 mole to about 1.2 moles per mole ofcupric chloride.

A solvent may be supplied in an amount that is suitable to effectuatethe reaction between 5-nitrotetrazolate and formed copper(I). Forexample, water (or other solvent) may be supplied in an amount that issuitable to effectuate the reaction between a 5-nitrotetrazolate saltand a copper(I) salt. As a more specific example, water (or othersolvent) may be supplied in an amount that is suitable to effectuate thereaction between NaNT and formed cuprous chloride.

The reaction components may be combined in any order or sequencesuitable to effectuate the reaction. By way of non-limiting example, thereaction of 5-nitrotetrazolate salt and formed copper(I) salt may becarried out by adding an aqueous solution of 5-nitrotetrazolate salt toan aqueous suspension of copper(II) salt and adding a suitable reducingagent, or vice versa.

The copper(I) nitrotetrazolate formed by the reaction of cupric salt(for example, cupric chloride), a reducing agent (for example sodiumascorbate), water and 5-nitrotetrazolate salt (for example, sodium5-nitrotetrazolate) may be a precipitate. The precipitate may beseparated by a suitable method known to those of skill in the art.Alternatively, the precipitate may be separated by filtration. As yetanother alternative, the precipitate may be separated using a flotationtechnique. It may be desirable to separate finer or lighter precipitateparticles from coarser or heavier precipitate particles (for example,the coarser or heavier particles may be desirable from the standpoint ofeasy handling and loading). A flotation technique may be employed toachieve such a separation, as may other techniques known to those ofskill in the art. Alternatively, the fine particles may be removed bycareful decanting. Alternatively, the precipitate (which may, forexample, be a dark brown precipitate) is collected over filter paper.

The precipitate formed by the reaction of cupric salt (for example,cupric chloride), a reducing agent (for example sodium ascorbate), waterand 5-nitrotetrazolate salt (for example, sodium 5-nitrotetrazolate) maybe washed. For example, the product may be washed either a single timeor multiple times with water. Alternatively, the product may be washedeither a single time or multiple times with alcohol, for example,isopropanol. Alternatively, the product may be washed in multiple stepsand in any order with both water and alcohol. For example, the productmay be washed sequentially with water and then isopropanol. The productmay then be dried. For example, the product may be air dried.Alternatively the product may be dried in an oven at 65 to 80° C.

The present application also contemplates products made by the methodsdescribed above. In other words, the present application contemplatesproducts made by reacting cupric salt (for example, cupric chloride),5-nitrotetrazolate salt (for example, sodium 5-nitrotetrazolate), and areducing agent (for example sodium ascorbate) in water, under theconditions and component quantities described above.

The products contemplated and made by the methods of the presentapplication (in at least some aspects of the present subject matter,copper(I) nitrotetrazolate) are free of lead and have been foundsuitable for use as explosives and, in particular, as primaryexplosives. Thus, the present application also contemplates methods forpreparing compounds suitable for use as primary explosives, andexplosive devices employing such compounds. Benefits include low cost,ease of preparation and low toxicity waste streams and health benefitsassociated with low lead materials in both military and commercialapplications.

The products contemplated and made by the methods of the presentapplication (including copper(I) nitrotetrazolate) exhibit a crystallinestructure that is suitable for loading and handling.

The foregoing is provided for purposes of illustrating, explaining, anddescribing embodiments of the present invention. Further modificationsand adaptations to these embodiments will be apparent to those skilledin the art and may be made without departing from the scope or spirit ofthe invention.

EXAMPLES

The following examples demonstrate the preparation and characterizationof a material as taught herein.

Example 1

Copper(I) nitrotetrazolate was prepared as follows. To 100 mL of astirred hot (95-100° C.) aqueous solution of copper(II) chloride (0.79g, 0.008 mol) and sodium 5-nitrotetrazolate dihydrate (1.70 g, 0.0096mol) in a 250 mL beaker was added 8 mL of a 0.5 molar aqueous solutionof sodium ascorbate at a rate of 1 mL/minute using a syringe pump. Afterthe eight minute addition, the reaction mixture was boiled for anadditional two minutes. The precipitate that was formed was collected onWhatman No. 1 filter paper, washed three times with water, twice withisopropanol, and then dried in a convection oven at 70° C. The yield ofsmall red rust crystals was 1.218 g (85.7%).

The results of a differential scanning calorimetry (DSC) analysis on thesolid are shown in FIG. 1. The results of a Fourier Transform InfraredSpectroscopy (FTIR) analysis on the solid are shown in FIG. 2.

Example 2

Copper(I) nitrotetrazolate was prepared as follows. To 100 mL of astirred hot (95-100° C.) aqueous solution of copper(II) chloride (0.79g) and sodium 5-nitrotetrazolate dehydrate (1.70 g) in a 250 mL beakerwas added 8 mL of a 0.5 molar aqueous solution of ascorbic acid at arate of 1 mL/minute using a syringe pump. After the eight minuteaddition, the reaction mixture was boiled for an additional two minutes.The precipitate that formed was collected on Whatman No. 1 filter paper,washed three times with water, twice with isopropanol, and then dried ina convection oven at 70° C.

While the present subject matter has been described and illustrated byreference to particular embodiments, it will be appreciated by those ofordinary skill in the art that the subject matter lends itself to manydifferent variations not illustrated herein. For these reasons, then,reference should be made solely to the appended claims for purposes ofdetermining the true scope of the present invention.

Although the appendant claims have single appendencies in accordancewith U.S. patent practice, each of the features in any of the appendantclaims can be combined with each of the features of other appendantclaims or the main claim.

What is claimed is:
 1. Copper(I) nitrotetrazolate, wherein copper(I) hasone valence electron, prepared by a process comprising the steps of: (a)combining cupric chloride, water, and sodium 5-nitrotetrazolate to forma mixture; (b) heating the mixture; (c) adding a solution of sodiumascorbate to the mixture; and (d) heating the solution of sodiumascorbate and the mixture.
 2. The copper(I) nitrotetrazolate of claim 1characterized by a Differential Scanning Calorimetry curve with adistinguishing peak at about 335 degrees C.
 3. The copper(I)nitrotetrazolate of claim 1 characterized by a Differential ScanningCalorimetry curve substantially as shown in FIG.
 1. 4. The copper(I)nitrotetrazolate of claim 1 characterized by a Fourier TransformInfrared Spectroscopy spectra with distinguishing peaks at about 1560,1487, 1456, 1423, and
 1327. 5. The copper(I) nitrotetrazolate of claim 1characterized by a Fourier Transform Infrared Spectroscopy spectra asshown in FIG. 2.